Electric motor and brake assembly

ABSTRACT

An electric brake assembly for a planetary reduction drive includes a first housing defining a brake housing compartment, first and second stators disposed within the brake housing compartment, and a rotor disposed within the brake housing compartment between the first and second stators. The rotor has a spline engaging an output shaft of a motor. The electric brake assembly also includes a brake end cap coupled to the first housing and defining a cylindrical volume, a plug movably disposed in the cylindrical volume of the brake end cap, a spring disposed within the cylindrical volume of the brake end cap and compressed by the plug to apply a spring biasing force for pressing the second stator against the rotor, and an electric brake coil positioned adjacent to the second stator to electromagnetically pull the second stator away from the rotor when energized.

CROSS-REFERENCE

This application is a continuation-in-part of U.S. patent applicationSer. No. 16/457,243, filed on Jun. 28, 2019, which claims the benefit ofU.S. Provisional Patent App. No. 62/692,256, filed on Jun. 29, 2018.These applications are incorporated herein by reference in theirentirety.

BACKGROUND OF THE INVENTION

This application relates to an electric planetary reduction driveincorporating an electric motor having a gear drive. Such a drive may beused for applications such as a ground drive for a scissors lift, boomlift or the like, although other applications are possible.

SUMMARY OF THE INVENTION

A compact planetary gear drive for an electric motor is disclosedherein. This design provides for a compound planetary gear assemblyproviding a summative reduction of the rotational speed of the electricmotor output to an output hub. One benefit of the disclosed design is areduced overall size and length of the drive. By way of example only,the planetary gear assembly is disposed entirely in the output hub toreduce envelope size. A further benefit of the drive disclosed herein isa limit on the amount of rollback in a vehicle in which the drive isused as a ground drive, which may be accomplished by limiting backlashin the drive. Various improvements for accomplishing these objectivesare disclosed herein. Further benefits and features of the disclosureare set forth herein.

A better understanding of the invention will be obtained from thefollowing detailed descriptions and accompanying drawings, which setforth illustrative embodiments that are indicative of the various waysin which the principles of the invention may be employed.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an external elevational view of an electric motor assemblyincluding a planetary gear drive, in accordance with the disclosureherein.

FIG. 2 is a cross-sectional view of the electric motor assembly of FIG.1, along the line 2-2. It will be understood that certain elements ofthe assembly, such as brake 112 and power and control module 114 seen inFIG. 1, are not depicted in FIG. 2 for clarity.

FIG. 3 is an exploded view of certain components of the electric motorassembly of FIG. 1.

FIG. 4 is an exploded view of certain components of the planetary gearassembly of the electric motor assembly of FIG. 1.

FIG. 5 is a perspective view of an electric motor assembly in accordancewith a second embodiment of the disclosure herein.

FIG. 6 is an external elevational view of the electric motor assembly ofFIG. 5.

FIG. 7 is a cross-sectional view of the electric motor assembly of FIG.5, along the line 7-7.

FIG. 8 is a perspective view of the electric motor assembly of FIG. 5,with certain external components removed for clarity.

FIG. 9 is a partially exploded perspective view of the electric motorassembly of FIG. 5.

FIG. 10 is a cross-sectional view similar to that of FIG. 7, butdepicting an electric motor assembly in accordance with a thirdembodiment of the disclosure herein.

FIG. 11 is a cross-sectional view similar to that of FIG. 7, butdepicting an electric motor assembly in accordance with a fourthembodiment of the disclosure herein.

FIG. 12 is a perspective view of an electric motor assembly inaccordance with a fifth embodiment of the disclosure herein.

FIG. 13 is an external elevational view of the electric motor assemblyof FIG. 12.

FIG. 14 is a cross-sectional view of the electric motor assembly of FIG.13, along the line 14-14.

FIG. 15 is a perspective view of the electric motor assembly of FIG. 12,with certain external components removed for clarity.

FIG. 16 is a perspective view of a planetary gear assembly of theelectric motor assembly of FIG. 12.

FIG. 17 is an exploded view of the planetary gear assembly of FIG. 16.

FIG. 18 is an exploded view of the planetary gear assembly of FIG. 16,rotated 90 degrees in relation to the view of FIG. 17.

FIG. 19 is an external elevational view of the planetary gear assemblyof FIG. 16.

FIG. 20 is a cross-sectional view of the planetary gear assembly of FIG.16, along the line 20-20.

FIG. 21 is a perspective view of a brake assembly, housing components,and certain electrical components of the electric motor assembly of FIG.12.

FIG. 22 is a perspective view of an electrical compartment cover andseals of the electric motor assembly of FIG. 12.

FIG. 23 is an exploded view of the brake assembly of FIG. 12.

FIG. 24 is an external elevational view of an electrical connector ofthe electric motor assembly of FIG. 12.

FIG. 25 is a top plan view showing a pin layout of the electricalconnector of FIG. 24.

FIG. 26 is a chart listing the pins of the pin layout shown in FIG. 25.

FIG. 27 is a cross-sectional view of a portion of an electric motorassembly in accordance with a sixth embodiment of the disclosure herein.

FIG. 28 is a cross-sectional view of an optional configuration formounting a stationary gear set similar to the stationary gear set shownin FIG. 27.

FIG. 29 is a perspective view of the optional configuration for mountingthe stationary gear set shown in FIG. 28.

DETAILED DESCRIPTION OF THE DRAWINGS

The description that follows describes, illustrates and exemplifies oneor more embodiments of the invention in accordance with its principles.This description is not provided to limit the invention to theembodiment(s) described herein, but rather to explain and teach theprinciples of the invention in order to enable one of ordinary skill inthe art to understand these principles and, with that understanding, beable to apply them to practice not only the embodiment(s) describedherein, but also any other embodiment that may come to mind inaccordance with these principles. The scope of the invention is intendedto cover all such embodiments that may fall within the scope of theappended claims, either literally or under the doctrine of equivalents.

It should be noted that in the description and drawings, like orsubstantially similar elements may be labeled with the same referencenumerals. However, sometimes these elements may be labeled withdiffering numbers or serial numbers in cases where such labelingfacilitates a more clear description. Additionally, the drawings setforth herein are not necessarily drawn to scale, and in some instancesproportions may have been exaggerated to more clearly depict certainfeatures. As stated above, this specification is intended to be taken asa whole and interpreted in accordance with the principles of theinvention as taught herein and understood by one of ordinary skill inthe art.

An electric planetary reduction drive 110 as depicted in FIG. 1 includesa housing comprising a main housing 130 joined to motor housing 120 viafasteners 118 and using a seal 119. A spring biased electric brake 112and power and control module 114 are attached to motor housing 120, andsplines 125 b are provided on output shaft 125 to engage electric brake112. As will be explained in more detail, output hub 140 also serves asa planetary reduction housing, and includes standard wheel mountingfasteners 141 and wheel mounting flange 140 a such that it can serve asa wheel hub.

As shown most clearly in FIGS. 2 and 3, a brushless electric motor 121is disposed in motor housing 120, and comprises stator 122, rotor 123and magnets 124. An output shaft 125 extends through motor 121 and issupported by a pair of bearings 126. Seals 127 are also providedadjacent the bearings 126. Splines 125 a are provided on output shaft125 to engage sun gear 151 as discussed below. As noted above, controlmodule 114 and brake 112 are not depicted in the cross-sectional view ofFIG. 2. Hall effect board 116 is also mounted to a surface of motorhousing 120 in a manner to be appropriately located with regard tomagnets 124. Wave spring 129 is disposed between bearing 126 and mainhousing 130 to provide an axial biasing force to the rotor 123 to keeprotor 123 biased towards Hall effect board 116 at start-up.

The structure of main housing 130 can be seen most clearly in FIG. 3.Main housing 130 includes a through opening 130 a for output shaft 125.Seal 133 is disposed between output hub 140 and main housing 130.Bearing 132 is disposed in main housing 130. Retaining ring 143 ismounted in groove 130 c and maintains ball bearing 142 in the properlocation on bearing land 130 b. It will be seen in FIG. 2 that shoulder140 d engages bearing 132, and shoulder 140 c engages bearing 142, in amanner to retain the axial location of output hub 140.

A fixed ring gear 135 having an anti-rotation opening 135 a is disposedinternal to output hub 140 in a clearance pocket 140 b, and mounted on acorresponding anti-rotation form 130 d on main housing 130. While a hexis depicted for the anti-rotation forms, it will be understood thatother shapes could be used.

Planetary gear assembly 150 comprises a pair of carrier plates 154connected via carrier plate screws 156 extending through through-holes154 b and retained by carrier plate nuts 157. A plurality of recesses154 d is provided to accommodate the carrier plate nuts 157 to reduceenvelope size for the carrier assembly. A projection pin 154 c is formedon one of a plurality of projections 154 a on each carrier plate 154 andengages a corresponding projection pin opening 154 f on one of theprojections 154 a on the other carrier plate 154. As shown in FIG. 4, anextra pin opening 154 f for the projection pins 154 c is provided on oneof the projections 154 a to improve ease of assembly by allowingassembly in different positions. Sun gear 151 is mounted on output shaft125 by means of splines 125 a. Sun gear 151 drives the plurality ofplanet gears 152, each of which comprises a first stage gear form 152 aand second stage gear form 152 b. Planet gears 152 are each mounted on arespective carrier pin 153. Each carrier pin 153 is preferably composedof steel and has an optional raised spline 153 a at each end to engagewith pin support holes 154 e of carrier plates 154. If carrier plates154 are composed of, for example, aluminum, the raised splines 153 awill deform the material adjacent its respective pin support holes 154 eduring assembly to assist in retaining carrier pins 153 in anon-rotatable fashion to reduce wear.

As seen most clearly in FIG. 2, planetary gear assembly 150 is disposedentirely within output hub 140. Retention plate 160, seal 161 andretaining ring 162 engage a portion of output hub 140 to assist inretaining the planetary gear assembly 150 in output hub 140. Secondstage gear forms 152 b engage and rotate against fixed ring gear 135,whereas first stage gear forms 152 a engage and drive rotating ring gear144, which is formed on or as part of output hub 140. It will beunderstood that ring gear 144 could be press fit into output hub 140 tosimplify assembly, but it will also be understood that maintaining aproper press fit between ring gear 144 and output hub 140 withoutslippage under expected torque loads would be difficult. It will also beunderstood that planetary gear assembly 150 will rotate in the samedirection as output shaft 125, whereas planet gears 152 will rotate inthe opposite direction, such that planetary gear assembly 150 acts asboth a speed reducer and torque amplifier for output hub 140.

A second embodiment of an electric planetary reduction drive 210 isdepicted in FIGS. 5-9. As seen in FIG. 5, a housing comprising a mainhousing 230 is joined to a second housing component 220 and motor statorhousing 217 via fasteners 218. An electric brake 212 and power andcontrol module 214 are attached to second housing component 220. Controlmodule 214 includes a connector 214 a for connection to a vehiclecontrol system as may be required, and the connector 214 a andassociated Hall effect board (similar to Hall effect board 116 to whichthe connector 214 a is wired) may be CAN-Bus capable when used with aCAN-Bus system. Power terminals 214 b provide the necessary powerinputs.

Output hub 240 also serves as a planetary reduction housing, andincludes standard wheel mounting fasteners 241 and wheel mounting flange240 a such that it can serve as a wheel hub.

As shown most clearly in FIGS. 7 and 8, electric motor 221 is disposedin motor stator housing 217 and second housing component 220, andcomprises stator 222, rotor 223 and a skewed magnet rotor assembly 211having skewed magnets 224. Motor stator housing 217 can be a finnedaluminum extrusion cut to a length dependent upon the number oflaminations combined to form the stator 222. An output shaft 225 extendsthrough electric motor 221 and is supported by a pair of bearings 226. Aseal 227 is provided adjacent one of the pair of bearings 226. Splines225 a are provided on output shaft 225 to engage sun gear 251 asdiscussed below. A Hall effect board (not shown, but similar to Halleffect board 116) is also mounted to a surface of second housingcomponent 220. Wave spring 229 is disposed between one of the pair ofbearings 226 and main housing 230 to provide an axial biasing force tothe rotor 223 to keep rotor 223 biased towards the Hall effect board atstart-up, as discussed above.

Planetary gear assembly 250 comprises a pair of carrier plates 254connected by means of carrier plate screws 256 and carrier plate nuts257, and a plurality of carrier pins 253. Raised splines such as splines153 a are optional. Sun gear 251 is mounted on output shaft 225 by meansof splines 225 a and retaining ring 249. Retaining ring 249 assists inlocating sun gear 251 and preventing contact with gear cover 260,described below. Flanged washer 255 is also provided between one of thecarrier plates 254 and cover plate 260. Sun gear 251 drives theplurality of planet gears 252, each of which comprises a first stagegear form 252 a and second stage gear form 252 b, and second stage gearform 252 b may be slip fit or press fit into first stage gear form 252a. Planet gears 252 are each mounted on a respective carrier pin 253.

As seen in, e.g., FIGS. 7 and 9, planetary gear assembly 250 is disposedentirely within output hub 240 and comprises a first stage ring gear 244and a fixed second stage ring gear 235. A difference from the firstembodiment lies with the connection of first stage ring gear 244 andoutput hub 240. Small projections 244 b on ring gear 244 with clearancefit into corresponding slots 240 b in the output hub 240 can provide ananti-rotation feature but will necessarily add rotational backlashbetween the ring gear 244 and the output hub 240.

As noted before, it is desirable to minimize backlash, which isgenerated by various clearances within the system, including clearanceat the brake rotor spline 225 b, sun gear spline 225 a, the mesh of sungear 251, the mesh of the large planet gear 252 a to large ring gear 244and the mesh of small planet gear 252 b to ring gear 235. In the secondembodiment, the large ring gear 244 is clamped between gear cover 260and output hub 240 by means of fasteners 262 extending through fastenerrecesses 244 a formed on ring gear 244. This clamping arrangement allowsthe use of standard slip fit tolerances while eliminating thisadditional backlash between ring gear 244 and output hub 240.

Main housing 230 includes spindle 230 b and attachment bores 230 a forconnecting ring gear 235 thereto via openings 235 a by means offasteners 236. This direct connection of ring gear 235 to main housing230 also eliminates another source of backlash and improves performance.

Second stage gear forms 252 b engage and rotate against fixed ring gear235, whereas first stage gear forms 252 a engage and drive rotatingfirst stage ring gear 244, which is attached to and thereby causesrotation of the output hub 240. Thrust washers 258 and 259 are disposedbetween carrier plates 254 and first stage gear 252 a and second stagegear 252 b, respectively. It will be understood that planetary gearassembly 250 will rotate in the same direction as output shaft 225,whereas planet gears 252 will rotate in the opposite direction, suchthat planetary gear assembly 250 acts as both a speed reducer and torqueamplifier for output hub 240.

Bearing 232 is disposed between main housing 230 and output hub 240,while needle roller bearing 242 is disposed between output hub 240 andspindle 230 b of main housing 230. The inner race 242 a of needle rollerbearing 242 is retained by ring gear 235. Hub seal 228 and spindle seal247 are provided to create the necessary seals, and retaining rings 245,246 are used to assist in retaining proper alignment of the components.

As seen most clearly in FIGS. 5, 6, 7 and 8, electric brake assembly 212is primarily disposed inside a brake housing compartment defined bysecond housing component 220 and brake housing 231, which is secured tosecond housing component 220 by fasteners 269. Brake assembly 212comprises a brake rotor 213 secured to splines 225 b formed on outputshaft 225. A pair of stators 215 a and 215 b is used to provide brakingforce to brake rotor 213. As seen in FIGS. 5 and 8, an electricalconnector 212 a connects brake 212 to an external power source and/orcontrol system, and coil 234 is energized to remove the braking forcefrom stators 215 a and 215 b. When coil 234 is deenergized, brakeplunger 238 bears against stator 215 a to translate stator 215 a in anaxial direction toward brake rotor 213, with compression spring 239providing the bias force. External manual brake release lever 237 isoperable to overcome the bias force of compression spring 239 anddisengage brake 212.

Output shaft 225 has a portion 225 c having a reduced diameter from therest of the shaft 225. When drive 210 is under load, for example whenused as a vehicle drive and the vehicle weight is applied thereto,output hub 240 will deflect with respect to main housing 230 and canflex output shaft 225. The reduced diameter portion 225 c of outputshaft 225, which is preferably approximately 40% of the main portion,allows such flexing with reduced stress.

Upper oil fill port 264 a and lower oil fill port 264 b are provided tofill the chamber in which planetary gear assembly 250 is disposed. Thesefill ports 264 a, 264 b are located on cover plate 260 to act as drainswhen output hub 240 is rotated such that they are located at the bottom,and act as level indicators when output hub 240 is rotated such thatthey are vertically aligned.

A third embodiment of an electric planetary reduction drive 310 isdepicted in FIG. 10. Elements of this embodiment that are identical orsubstantially identical with those of the second embodiment are givenidentical numerals and will not be discussed herein. By way of exampleonly, planetary gear assembly 250 is the same as previously discussed.Spacer or washer 348 bears against the inner races of bearing 332 andneedle roller bearing 342 (both of which are located internal to hub340) to assist in retaining the inner races of bearings 332 and 342 inan axial direction with respect to housing 330. Needle roller bearing342 is disposed between output hub 340 and spindle 330 b. Retaining ring345 holds bearing 332 axially in place within output hub 340 while seal333 is located external to the output hub 340, similar to seal 133. Thisinternal positioning of both bearing 332 and needle roller bearing 342,and use of a spacer 348 between the inner race of bearing 332 and needleroller bearing 342, eliminates the need for an equivalent of retainer246 used in the prior embodiment, wherein bearing 232 was locatedexternal to the hub 240 and needle roller bearing 242 was locatedinternal to the output hub 240. This eases assembly, as retainer 246 ofthe previous embodiment can be challenging to access. Output shaft 325is modified slightly to accommodate the changes to the shapes of othercomponents, and has a smaller diameter portion 325 c as notedpreviously, a spline 325 a to engage the sun gear 251 of planetary gearassembly 250, and a brake spline 325 b to engage brake rotor 213 asdiscussed above.

A fourth embodiment of an electric planetary reduction drive 410 isdepicted in FIG. 11. As with the third embodiment, elements that areidentical or substantially identical with those of the second embodimentare given identical numerals and will not be discussed herein. By way ofexample only, planetary gear assembly 250 is the same as previouslydiscussed. Motor output shaft 425 is modified slightly to accommodatechanges to other components, and comprises a planetary gear spline 425a, a brake spline 425 b and a reduced diameter portion 425 c. Ring gearbearing 442, which preferably is a needle bearing, is mounted in outputhub 440 on the outer diameter of ring gear 435, and output hub 440 thusruns on this ring gear bearing 442 and the outer diameter of ring gear435. The ball bearing 432 with retaining rings 445 and 446 provides theaxial retention between the main housing 430 and the output hub 440. Thering gear 435 is affixed to the main housing 430 with fasteners 436while the spindle seal 447 and hub seal 428 provide the sealing betweenthe main housing 430 and the output hub 440. As in prior embodiments,output hub 440 includes standard wheel mounting fasteners 241 and wheelmounting flange 440 a such that it can serve as a wheel hub. One ofskill in the art will realize that the size, number and placement of thefasteners disclosed herein, as well as the selection of the bearingsdisclosed herein, will vary depending on factors such as the expectedload. In this embodiment, outboard bearing 442 is located closer toflange 440 a such that bearing 442 is in the load plane of the wheel(not shown) attached to flange 440 a, thereby reducing the reaction loadon inboard bearing 432. This allows a shorter distance between thesebearings thus reducing the overall length of the motor compared to theother embodiments.

A fifth embodiment of an electric planetary reduction drive 510 isdepicted in FIGS. 12-23. As seen in FIGS. 12-14, a housing comprises amain housing 530, a motor stator housing 517, a motor end cap 520, and abrake housing 531. The main housing 530 is joined to a motor end cap 520(also referred to as a “first housing” or a “second housing component”)via fasteners 518. The motor stator housing 517 is interposed betweenmain housing 530 and motor end cap 520. Motor stator housing 517 ispreassembled to motor end cap 520 by means of fasteners 568. An electricbrake 512, partially housed in brake housing 531 (also referred to as a“brake end cap”), is attached to the opposite end of motor end cap 520by means of fasteners 569 and sealed by a brake cover gasket 570.

An electrical connector 514 is attached or mounted to an electricalcompartment cover 573, which is secured to an electrical compartment 520a integrally formed on motor end cap 520. As illustrated in FIGS. 12 and21-22, the electrical connector 514 is housed within the electricalcompartment and partially extends through a connector mounting opening573 b defined by the electrical compartment cover 573. The electricalconnector 514 is coupled to the electrical compartment cover 573 bythreadably coupling the electrical connector 514 to a jam nut 577. Theelectrical connector body 514 a includes external threads to threadablycouple with the internal threads of jam nut 577. The electricalcompartment cover 573 is removably coupled to the electrical compartment520 a via fasteners 574.

Electrical connector 514 comprises motor power phase terminals, brakecoil terminals and motor control terminals and is configured forconnection to a vehicle control system as may be required. An electricbrake coil 534 of electric brake 512 is connected to electricalconnector 514 via brake electrical conductors 512 b and connector 512 ashown in FIGS. 15 and 23. The motor control terminals are electricallyconnected to a Hall effect board 516 shown in FIGS. 14 and 21. Most ofthe electrical conductors, such as basic wiring and motor phasewindings, are omitted to simplify and improve clarity of theillustrations.

As shown in FIG. 24, electrical connector 514 comprises a connector body514 a, a brake wiring harness with brake connector 514 b, and a Hallboard wiring harness with Hall board connector 514 c. Brake connector514 b engages mating brake connector 512 a; Hall board connector 514 cengages a mating connector (not shown) of Hall board 516. The brakeconnector 514 b connects to the mating brake connector 512 a toelectrically connect one or more pins of the connector body 514 a to theelectric brake coil 534 of the electric brake 512. The Hall boardconnector 514 c connects to a mating connector of the Hall effect board516 to electrically connect other pin(s) of the connector body 514 a tothe Hall effect board 516.

Connector pins disposed or housed in connector body 514 a of electricalconnector 514 are shown in FIG. 25 and a corresponding chart of thesepins for an exemplary embodiment is provided in FIG. 26. Pins withdesignation “1,” “2” and “3” in FIGS. 25 and 26 supply power,respectively, to three motor phase windings (“PHASE A,” “PHASE B” and“PHASE C”) of the electric motor stator 522. Pins labeled “4” and “5”provide, respectively, power (“BRAKE+V”) and ground (“BRAKE GND”)connections to the electric brake coil 534 via brake connector 514 b andrespective wiring. Pins labeled “6,” “7,” “8,” “9,” “10” and “11” areconnected respectively, via Hall board connector 514 c and respectivewiring, to a temperature sensor (“TEMP”), a first Hall Sensor (HALL“A”), a second Hall sensor (“HALL B”), a Hall board ground terminal(“HALL GND”), a third Hall sensor (“HALL C”), and a Hall board powerterminal (“+V”), all of Hall board 516. In other words, Pins #1-3 aredesignated for conducting power for the electric motor 521, pins #4-5 isdesignated for a control voltage to control operation of the electricbrake 512, and pins #6-12 are designated for electrically connecting tothe Hall effect board 516. Additionally, the connector body 514 adefines apertures through which the respective pins extend. In theillustrated example, pins #1-3 are detachable from the connector body514 a through the respective ones of the apertures. Alternatively, pins#1-3 may be fixedly connected (e.g. via glue) to the connector body 514a with lead wires permanently attached to electric motor 521. Pins #4-11are fixedly connected (e.g., via glue) to the connector body 514 a. Itshould be understood that the particular arrangement and association ofpins #4-11 may be revised.

Referring to FIGS. 12, 13, 14 and 21-23, the electrical compartmentcover 573 includes connector guards 573 a adjacent to mounting opening573 b. The connector guards 573 a are guard walls that have a heightthat extends beyond that of the electrical connector 514 to protectelectrical connector 514 when it is installed in connector mountingopening 573 b. The connector guards 573 a are spaced apart from themounting opening 573 b by a distance that provides access to theelectrical connector 514 and jam nut 577 to enable a person to attach ordetach electrical connector 514 to or from electrical compartment cover573. An inner gasket 575 engages an inner surface of the electricalcompartment cover 573 about the connector mounting opening 573 b to sealthe joint between electrical connector 514 and electrical compartmentcover 573, while an outer gasket 576 is installed in outer seal groove573 c between electrical compartment cover 573 and electricalcompartment 520 a to seal the joint between electrical compartment cover573 and electrical compartment 520 a. Electrical compartment cover 573defines outer seal groove 573 c in which outer gasket 576 is at leastpartially positioned. An interface surface 573 d defined by perimeterrim 573 e of electrical compartment cover 573 contacts a mating surface520 g defined by electrical compartment 520 a to limit compression ofouter gasket 576. Perimeter rim 573 e overlaps a raised seal land 520 hof electrical compartment 520 a to protect outer gasket 576 whilesecurely and accurately positioning electrical compartment cover 573 onelectrical compartment 520 a to (1) facilitate installation of fasteners574 by facilitating alignment between electrical compartment cover 573and electrical compartment 520 a and (2) to protect outer gasket 576that is positioned between electrical compartment cover 573 andelectrical compartment 520 a.

Flange 530 d of main housing 530 defines a plurality of drive unitmounting holes 530 c to attach electric planetary reduction drive 510 toa frame structure such as a vehicle frame. As in prior embodimentsdepicted herein, output hub 540 also serves as the planetary reductionhousing of planetary reduction drive 510, and includes standard wheelmounting fasteners 541 and wheel mounting flange 540 a such that it canserve as a wheel hub. Output hub 540 has a first hub end that extendsbeyond fixed ring gear 535 and a second hub end that extends towardflange 530 d of main housing 530. Hub cap or gear cover 560 is attachedto the first hub end of the output hub 540, by means of a plurality offasteners 562, to cover planetary gear assembly 550. Gear cover 560defines through-holes and the first hub end of output hub 540 definesthreaded-holes that receive fasteners 562 to couple gear cover 560 tooutput hub 540. This joint is sealed by means of dodecagon (12-sided)seal 561. Similar to the second embodiment described herein, gear cover560 includes a pair of oil fill ports 564 (with plugs).

As shown most clearly in FIGS. 14 and 15, electric motor 521 is disposedin motor stator housing 517 and motor end cap 520. Electric motor 521includes a stator 522 and a skewed magnet rotor assembly 511. Rotorassembly 511 comprises a pair of rotor components 523 and a set ofskewed magnets 524. As shown in FIG. 21, the Hall effect board 516 (withassociated spacers or standoffs 516 a) is mounted on machinedplatform(s) 520 f formed on motor end cap 520 to precisely position theHall effect board 516 in close proximity to the rotor magnets 524. Anoutput shaft 525 extends through, is coupled to, and is driven byelectric motor 521 and is supported by a pair of bearings 526. A seal527 is provided adjacent one of the pair of bearings 526, which isdisposed in the aperture 530 e of spindle 530 b between the output shaft525 and an inner surface of the spindle 530 b, to partition and protectthe electrical components from the gearing lubricant. Splines 525 a areprovided on one end of output shaft 525 to engage a sun gear 551 ofplanetary gear assembly 550 to enable output shaft 525 to drive sun gear551 and, more generally, planetary gear assembly 550. Splines 525 b areprovided on the opposite end of output shaft 525 to engage brake hub 571rotor 513. Output shaft 525, similar to output shaft 225, includes areduced diameter portion 525 c to allow flexing with reduced stress.Knurling 525 d is provided on output shaft 525 for press-fit engagementof two identical motor rotor components 523. Each rotor component 523carries half of the motor magnets 524. One of the pair of rotorcomponents 523 is rotated a precise number of degrees in relation to theother and then this pair of skewed rotor components 523 is press-fitonto output shaft 525 to form the skewed magnet rotor assembly 511.Skewing the magnets in this manner reduces a cogging effect that isparticularly noticeable at low speeds, thereby providing a smootherrunning motor. In one embodiment, the optimum amount of skew betweenrotor components 523 is 3.75 degrees, but this will vary with electricmotor design (e.g. varying with the number of stator slots, rotor poles,etc.).

As shown in FIGS. 15-20, planetary gear assembly 550 includes an outercarrier plate 565 (also referred to as a “first gear carrier”)comprising a first plate 565 f, three cupped protrusions 565 a extendingtherefrom, and cylindrical projections 565 b each of which extends froma respective one of the cupped protrusions 565 a. An inner carrier plate566 (also referred to as a “second gear carrier”) comprises a secondplate 566 f and three mating cupped protrusions 566 a extendingtherefrom. Each of cupped protrusions 566 a defines a respective jointopening 566 b. During assembly, the cylindrical projections 565 b areinserted into the joint openings 566 b such that the joint openings 566b receive the cylindrical projections 565 b to couple the outer carrierplate 565 to the inner carrier plate 566. A portion of each cylindricalprojection 565 b that protrudes beyond the joint opening 566 b is thenupset or swaged to secure the joint connection to secure the outercarrier plate 565 to the inner carrier plate 566 via a swagedconnection. The cylindrical projections 565 b, the cupped protrusions565 a, and the first plate 565 f of the outer carrier plate 565 areintegrally formed together and the cupped protrusions 566 a and thesecond plate 566 f of the inner carrier plate 566 are integrally formedtogether to enable the outer carrier plate 565 to couple to the innercarrier plate 566 without separate fasteners via the swaged connection.The cupped protrusions 565 a of the outer carrier plate 565 and thecupped protrusions 566 a of the inner carrier plate 566 extend aroundthe sun gear 551 and planet gears 552 that are disposed between theouter carrier plate 565 and the inner carrier plate 566 to enable theouter carrier plate 565 and the inner carrier plate 566 to coupletogether via the swaged connection.

A carrier pin 553 extends axially from each of the planet gears 552. Thecarrier pins 553 supporting the respective planet gears 552 aresupported by and trapped between outer carrier plate 565 and innercarrier plate 566 during this joining process. Specifically, the ends ofeach carrier pin (or jack shaft) 553 are press-fit into support openings565 c, 566 c and retained by carrier pin retention features 565 e, 566 eto retain the planet gears 552 between the outer and inner carrierplates 565, 566. The carrier pins 553 and the support openings 565 c,566 c are sized to enable the support openings 565 c, 566 c to receivethe carrier pins 553 via press-fit. The support openings 565 c aredefined by the first plate 565 f of the outer carrier plate 565, and thesupport openings 566 c are defined by the second plate 566 f of theinner carrier plate 566.

Relief slits 565 d, 566 d are formed in the walls of the supportopenings 565 c, 566 c to prevent cracks from occurring during thepress-fit operation of the support openings 565 c, 566 c. The firstplate 565 f of the outer carrier plate 565 defines the relief slits 565d. Each of the relief slits 565 d is connected to a respective one ofthe support openings 565 c to deter cracks from forming in the outercarrier plate 565 when a respective one of the carrier pins 553 isreceived by the respective support opening 565 c via press-fit.Similarly, each of the relief slits 566 d is connected to a respectiveone of the support openings 566 c to deter cracks from forming in theinner carrier plate 566 when a respective one of the carrier pins 553 isreceived by the respective support opening 566 c via press-fit.

Sun gear 551 is mounted on an end of output shaft 525 by means ofsplines 525 a and retained by retaining ring 549. Sun gear 551 defines afirst axial opening having internal splines 551 a that receive externalsplines 525 a of output shaft 525 to couple sun gear 551 to output shaft525. In the illustrated example, inner carrier plate 566 defines asecond axial opening that enables output shaft 525 to extend throughinner carrier plate 566 and to sun gear 551 that is disposed betweeninner carrier plate 566 and outer carrier plate 565. Retaining ring 549assists in locating sun gear 551 and prevents contact with gear cover560. Flanged washer 555 is also provided between the outer carrier plate565 and gear cover 560. The planet gears 552 are disposed around andengage or are meshed with the sun gear 551. Sun gear 551 drives theplurality of planet gears 552, each of which comprises a first stagegear form 552 a and a second stage gear form 552 b adjacent first stagegear form 552 a. The second stage gear form 552 b has a smaller outerdiameter than that of the first stage gear form 552 a. The second stagegear form 552 b may be slip fit or press fit into the first stage gearform 552 a.

As seen in FIG. 14, planetary gear assembly 550 is disposed entirelywithin output hub 540 and includes a first stage ring gear 544 and afixed second stage ring gear 535. As in the second embodiment, the firststage ring gear 544 comprises projections 544 b that fit intocorresponding slots in the output hub 540 to provide an anti-rotationfeature. As also illustrated in the second embodiment, the large ringgear 544 is clamped between gear cover 560 and output hub 540 by meansof fasteners 562 extending through the fastener recesses 544 a formed onring gear 544.

In a further similarity with the second embodiment, main housing 530includes spindle 530 b and flange 530 d that extends radially outwardlyfrom the spindle 530 b. The spindle 530 b has first and second opposingends and defines an aperture 530 e extending axially between the firstand second ends. The output shaft 525 extends through the aperture 530 eof the spindle 530 b. Flange 530 d extends radially outward from thesecond end of the spindle 530 b. Fillet corners 530 f and 530 g areformed on surfaces of main housing 530 as shown. The spindle 530 bdefines threaded bores 530 a at the first end for connecting fixed ringgear 535 thereto by means of fasteners 536. The first end of the spindledefines the threaded bores 530 a and the fixed ring gear 535 definesmounting holes that align with the threaded bores 530 a to receive thefasteners 536. It should be noted that the planetary gear assemblies250, 550 are basically interchangeable with only minor modifications.

Second stage gear forms 552 b of the planet gears 552 are meshed with,engage, and rotate against fixed ring gear 535. The fixed ring gear 535is coupled to the first end of the spindle 530 b via the fasteners 536and is housed in the output hub 540. The fixed ring gear 535 also housesthe second stage gear forms 552 b such that the planet gears 552 are atleast partially disposed in the output hub 540. First stage gear forms552 a of the planet gears 552 engage and drive the rotating first stagering gear 544 that is attached to the output hub 540. The first stagegear forms 552 a of the planet gears 552 are meshed with the first stagering gear 544 to cause the output hub 540 to rotate about the spindle530 b. Referring to FIG. 20, thrust washers 558 are disposed between theouter carrier plate 565 and first stage gears 552 a, while thrustwashers 559 are disposed between inner carrier plate 566 and the secondstage gears 552 b. Planetary gear assembly 550 will rotate in the samedirection as output shaft 525, whereas planet gears 552 will rotate inthe opposite direction, such that planetary gear assembly 550 acts asboth a speed reducer and torque amplifier for output hub 540.

A stacked pair of hub bearings 542 is disposed on spindle 530 b of mainhousing 530 to bear loads transmitted through output hub 540 and supportrotation of output hub 540. The stacked pair of hub bearings 542 contacteach other. The stacked pair of hub bearings 542 are positioned radiallybetween an outer surface of the spindle 530 b and an inner surface ofthe output hub 540 and axially between the fixed ring gear 535 andflange 530 d of main housing 530 to facilitate rotation of the outputhub 540 about the spindle 530 b. An outer surface of each of the hubbearings 542 contacts the inner surface of the output hub 540, and aninner surface of each of the hub bearings 542 contacts the outer surfaceof the spindle 530 b. The inner races of the stacked pair of hubbearings 542 are clamped in place on spindle 530 b between ring gear 535and spacer ring 548 when fasteners 536 are installed in threaded bores530 a.

A first of the hub bearings 542 contacts spacer ring 548, and a secondof the hub bearings 542 contacts fixed ring gear 535. Spacer ring 548 ispositioned between and engages the first of the hub bearings 542 andmain housing 530 adjacent both of the fillet corners 530 f and 530 gthat assist in alleviating stresses on main housing 530. Spacer ring 548includes a body and a rim portion extending transversely therefrom.Output hub 540 is firmly secured against the outer race of the pair ofbearings 542 by retaining ring 546. Hub seal 528 and spindle seal 547(e.g., an O-ring seal) engage the spacer ring 548 to create the fluidseals. The spacer ring 548 comprises a compression face for the staticspindle seal 547 and a running surface for the dynamic hub seal 528.Spindle seal 547 is positioned between flange 530 d of main housing 530,the base of spacer ring 548, and the arm of spacer ring 548. The hubseal 528 is positioned radially between and engages the spacer ring 548and the inner surface of the output hub 540.

Retaining rings 545, 546 are arranged adjacent hub seal 528. Hub seal528 is positioned axially between the retaining rings 545, 546. Theretaining ring 545 is positioned adjacent to a first side of the hubseal 528, and the retaining ring 546 is positioned adjacent to a secondside of the hub seal 528. The retaining ring 545 extends radiallybetween the arm of the spacer ring 548 and the inner surface of theoutput hub 540. The retaining ring 546 is positioned between hub seal528 and a first of the hub bearings 542. Additionally, a portion of theretaining ring 546 is positioned in a retaining ring groove definedalong the inner surface of the output hub 540. To facilitate positioningof the retaining ring 546, the retaining ring groove is partiallydefined by a chamfered surface that receives and engages a chamferedsurface of the retaining ring 546.

Similar to brake assembly 212 and seen most clearly in FIGS. 14, 15 and23, electric brake assembly 512 is primarily disposed inside a brakehousing compartment defined by motor end cap 520 and brake housing 531,which is secured to motor end cap 520 by fasteners 569. Brake assembly512 comprises a brake rotor 513 disposed in the brake housingcompartment. The brake rotor 513 has a castellated inner diameter 513 athat is slidingly engaged to a castellated brake rotor hub 571. Thecastellated brake rotor hub 571 also comprises splines 571 a that areslidingly engaged to splines 525 b of output shaft 525. The axial lengthof brake rotor hub 571 and splines 571 a is significantly greater thanthe thickness of brake rotor 513. The greater axial length of brakerotor hub 571 ensures a robust interface between splines 571 a andsplines 525 b to withstand dynamic loading of this spline interface whenthe electric brake 512 is engaged. Brake rotor 513 is positioned betweenand adjacent to an inner stator 578 and an outer stator 579 within thebrake housing compartment. Stators 578 and 579 are configured to providea braking force to the brake rotor 513 under the influence ofcompression spring 539. Stators 578 and 579 comprise a plurality ofanti-rotation tabs 578 a and a plurality of anti-rotation tabs 579 a,respectively. Referring to FIG. 23, the plurality of anti-rotation tabs578 a is slidingly engaged to inner mating grooves 520 b, which aredefined by motor end cap 520 adjacent the brake housing compartment, toprevent rotation of stator 578 within the brake housing compartment. Theplurality of anti-rotation tabs 579 a is slidingly engaged to outermating grooves 520 c, which are defined by motor end cap 520 adjacentthe brake housing compartment, to prevent rotation of stator 579 withinthe brake housing compartment. The overall diameter (includinganti-rotation tabs) of the inner stator 578 is less than the overalldiameter (including anti-rotation tabs) of the outer stator 579. Thatis, the anti-rotation tabs 578 a, 579 a are stepped such that the tab579 a extends radially beyond the tab 578 a. Additionally, therespective grooves 520 b, 520 c are adjacent to one another and steppedin relation to one another such that the groove 520 c is larger than thegroove 520 b. The stepped configuration of the anti-rotation tabs 578 a,579 a and the stepped grooves 520 b, 520 c requires inner stator 578 tobe inserted into the brake housing compartment before outer stator 579,thereby preventing an incorrect stator assembly sequence. Ribs 520 d arealso defined by motor end cap 520 to further facilitate positioning ofthe stators 578, 579 within the motor housing compartment by ensuringthat the anti-rotation tabs 578 a, 579 a are aligned with grooves 520 b,520 c during assembly.

Electric brake coil 534 is positioned adjacent to outer stator 579. InFIG. 14, the electric brake coil 534 is disposed within acircumferential slot 531 c defined by the brake housing 531. Whenelectric brake coil 534 is energized via conductors 512 b (routedthrough opening 520 e formed in motor end cap 520), electric brake coil534 removes the braking force from stators 578 and 579 byelectro-magnetically pulling the outer stator 579 away from the brakerotor 513 and against the brake housing 531. That is, the electric brakecoil 534, when energized, applies an electro-magnetic force that isgreater than the spring biasing force to the outer stator 579 to releaseouter stator 579 from the brake rotor 513. When electric brake coil 534is de-energized, compression spring 539 applies a biasing force againstthrust washer 572, which bears against stator 579 to press thestator/rotor stack comprising stator 579, rotor 513 and stator 578against motor end cap 520. Inner stator 578 is formed of high-carbonsteel to limit an amount of wear caused by the brake rotor 513 and/or toprevent the electro-magnetic force of the electric brake coil 534 frommoving the inner stator 578. Outer stator 579 is positioned betweenelectric brake coil 534 and brake rotor 513 to facilitate theelectro-magnetic force in moving outer stator 579. Additionally, outerstator 579 is formed of low-carbon steel and/or is thicker than innerstator 578 to further facilitate the electro-magnetic force in movingouter stator 579.

Thrust washer 572 is positioned between and engages compression spring539 and outer stator 579 to facilitate application of the spring biasingforce to outer stator 579. Threaded aperture 531 a formed by brakehousing 531 and spring chamber 531 b form a cylindrical volume.Compression spring 539 is disposed in spring chamber 531 b adjacentthreaded aperture 531 a formed by brake housing 531. The diameters ofcompression spring 539 and spring chamber 531 b are larger than thediameter of threaded aperture 531 a, to prevent loss of compressionspring 539 through threaded aperture 531 a. An external brake releaseplug 537 is movably disposed in threaded aperture 531 a formed by brakehousing 531. Compression spring 539 is configured to engage and becompressed by brake release plug 537 to cause compression spring 539 toapply a spring biasing force against thrust washer 572 which bearsagainst stator 579 to compress the stator/rotor stack comprising stator579, rotor 513 and stator 578 against motor end cap 520. Brake releaseplug 537 is threadably coupled to brake housing 531 via threading. Brakerelease plug 537 can be loosened to position brake release plug 537 at alocation relative to brake housing 531 that reduces the biasing force.For example, the brake release plug 537 can be loosened via unthreadinguntil compression spring 539 disengages thrust washer 572 and/or outerstator 579 to enable a vehicle to be moved in a manual bypass mode when,for example, electrical power is unavailable. A cross-sectional view ofa sixth embodiment depicting an electric planetary reduction drive 610is shown in FIG. 27. The electric motor and brake assembly portion ofdrive 610 is cut away in FIG. 27, but may be the same as the previouslydescribed electric motor and brake assembly portion of electricplanetary reduction drive 510 shown in FIG. 14.

As seen in FIG. 27, a two-stage reduction gear arrangement 650 is housedor disposed entirely within output hub 640 and includes a single ringgear 635 that is fixed to and within output hub 640 and thereforerotates with output hub 640 about spindle 630 b. A motor output shaft625 is supported by a pair of bearings 626 (one shown). A seal 627 isprovided adjacent to one of the pair of bearings 626 to partition andprotect the electrical components from the gearing lubricant. The motoroutput shaft 625 includes a reduced diameter portion 625 c to allowflexing with reduced stress and splines 625 a are provided on one end ofmotor output shaft 625 to engage a first stage sun gear 651 of planetarygear arrangement 650. The first stage sun gear 651 is mounted on motoroutput shaft 625 by means of splines 625 a and retained by retainingring 649. That is, first stage sun gear 651 is coupled to and driven byoutput shaft 625.

The two-stage reduction gear arrangement 650 comprises a planetary firststage gear set and a stationary second stage gear set, as will bedescribed below. It should be noted that ring gear 635 may optionallycomprise two separate ring gears, one for each of these two gear sets,with both of these two separate ring gears fixed within output hub 640.Using two separate ring gears rather than a single ring gear 635 mayreduce manufacturing costs.

A plurality of first stage planetary gears 681 (the planetary firststage gear set) is driven by the first stage sun gear 651. The firststage planetary gears 681 are supported on support pins of a planetarygear carrier 667 with flanged bushings 683 interposed to reducerotational wear and provide axial force bearing surfaces. The firststage planetary gears 681 are meshed with first stage sun gear 651 andring gear 635. Planetary gear carrier 667 is drivingly engaged to asecond stage sun gear 663, which in turn drives a plurality of secondstage reduction gears 682 (the stationary second stage gear set) thatare rotationally mounted on stationary carrier pins 684. The secondstage reduction gears 682 are meshed with the second stage sun gear 663and ring gear 635. The stationary carrier pins 684 are supported inbores 630 c formed in spindle 630 b of main housing 630 and may bestaked in place, as shown, to ensure retention in spindle 630 b.

Main housing 630 includes spindle 630 b and a flange 630 d that extendsradially outwardly from spindle 630 b. Spindle 630 b has first andsecond opposing ends and defines an aperture 630 e extending axiallybetween the first and second ends. Output shaft 625, which is coupled toand driven by a motor, extends through the aperture 630 e of spindle 630b. The flange 630 d extends radially outward from the second end ofspindle 630 b. The bores 630 c from which stationary carrier pins 684extend are defined at the first end of spindle 630 b.

A magnet carrier 688 may be mounted in the aperture 630 e of spindle 630b at the first end. A plurality of magnets 689 can be retained by themagnet carrier 688 to capture any metal filings generated by thetwo-stage reduction gear assembly 650 to extend its service life. Asillustrated, the magnet carrier 688 is a tri-lobbed carrier that retainsthree magnets 689, but various numbers of magnets are contemplatedwithin the scope of the invention. Magnet carrier 688 includes a flangethat extends beyond and engages the first end of the spindle 630 b.Magnet carrier 688 is held in place by thrust washers 686 that arepositioned between and engage second stage reduction gears 682 and thelip of magnet carrier 688.

Flanged bushings 685 are interposed between the carrier pins 684 and thesecond stage reduction gears 682. Thrust washers 686 are positionedbetween the second stage reduction gears 682 and the inner bearing raceof the second bearing of the pair of hub bearings 642. The first stageplanetary gears 681 and the second stage reduction gears 682cooperatively drive ring gear 635 and hub 640.

Stacked pair of hub bearings 642 is disposed on spindle 630 b to bearloads transmitted through output hub 640 and to support rotation ofoutput hub 640. Stacked pair of hub bearings 642 is positioned radiallybetween an outer surface of spindle 630 b and an inner surface of outputhub 640. Stacked pair of hub bearings 642 includes a first bearing and asecond bearing that are arranged axially with respect to each other in aside-by-side manner. The inner races of the stacked pair of hub bearings642 are clamped in place on spindle 630 b by a plurality of fasteners687 (one shown) installed in threaded bores 630 a defined at the firstend of spindle 630 b, thereby retaining hub bearings 642 on spindle 630b. Fasteners 687 bear against the inner race of the second bearing ofthe pair of hub bearings 642, which in turn bear against a spacer ring648 that bears against main housing 630. Spacer ring 648 is positionedadjacent to the second end of spindle 630 b and between the firstbearing of the pair of hub bearings 642 and flange 630 d of main housing630. That is, the pair of hub bearings 642 is positioned axially betweenand engages spacer ring 648 and a combination of fasteners 687 and ringgear 635.

Spacer ring 648 extends to a curved outer surface of main housing 630.Hub seal 628 and spindle seal 647 (e.g., an O-ring seal) engage spacerring 648 to create the fluid seals. Spacer ring 648 comprises acompression face for the static O-ring seal 647 and a running surfacefor the dynamic hub seal 628. The spindle seal 647 is positioned betweenand engages the spindle 630 b, the spacer ring 648, and the firstbearing of the pair of hub bearings 642. The hub seal 628 includes a lipand is positioned radially between and engages the spacer ring 648 andthe inner surface of the output hub 640.

A hub cap or gear cover 660 is threaded on its periphery to engagemating threads formed on output hub 640. When gear cover 660 isthreadably coupled to output hub 640, gear cover 660 covers planetarygear arrangement 650 and bears against ring gear 635. In turn, ring gear635 bears against the outer race of one of the stacked pair of hubbearings 642, thereby forcing the stacked pair of hub bearings 642 tobear against output hub 640 in order to prevent and/or otherwise deter,in cooperation with fasteners 687, axial movement of output hub 640relative to spindle 630 b. Gear cover 660 also serves as a runningsurface for the flanged bushings 683 that support and protect theplanetary first stage gears 681.

Gear cover 660 is sealed to hub 640 by means of a peripheral O-ring seal661. Similar to other gear covers described herein, gear cover 660includes a pair of oil fill ports 664 (one shown).

FIGS. 28 and 29 depict an optional configuration for mounting astationary gear set similar in form and function to the stationarysecond stage reduction gears 682 shown in FIG. 27. In this optionalconfiguration, a pilot 730 a is formed on the distal end (also referredto as the “first end”) of spindle 730 b of main housing 730 to locate astationary carrier 790 that is attached to the spindle 730 b by means ofa plurality of fasteners 791. Main housing 730 includes spindle 730 band a flange 730 d that extends radially outwardly from spindle 730 b.Spindle 730 b has first and second opposing ends and defines an aperture730 e extending axially between the first and second ends. Output shaft725, which is coupled to and driven by an electric motor (not shown),extends through the aperture 730 e of spindle 730 b. The flange 730 dextends radially outward from the second end of spindle 730 b.

The stationary carrier 790 includes integrally formed gear support pins790 a on which second stage reduction gears 782 (one shown) arerotationally mounted with flanged bushings 794 interposed between thegear support pins 790 a and the second stage reduction gears 782. Theinstalled stationary carrier 790 bears against the outermost inner raceof the pair of hub bearings 742, which in turn bear against a spacerring 748 that bears against main housing 730. A spacer 793 and flangedwasher 792 provide thrust load bearing structure and a wear resistantrunning surface for the second stage sun gear 763. Fluid openings 793 aformed in spacer 793 ensure lubrication flow as needed. When installed,motor output shaft 725 passes through concentric openings formed inspacer 793, flanged washer 792 and second stage sun gear 763 to engage afirst stage sun gear (not shown, but similar to sun gear 651) by meansof splines 725 a formed thereon. First stage sun gear is coupled to anddriven by output shaft 725.

The pair of hub bearings 742 is disposed on spindle 730 b to bear loadstransmitted through an output hub and to support rotation of the outputhub about the spindle 730 b. The pair of hub bearings 742 is positionedradially between an outer surface of spindle 730 b and an inner surfaceof the output hub. The pair of hub bearings 742 includes a first bearingand a second bearing that are arranged axially with respect to eachother in a side-by-side manner. Stationary carrier 790 engages thesecond bearing, and spacer ring 748 engages the first bearing. Spacerring 748 is positioned adjacent to the second end of spindle 730 b andbetween the first bearing and the flange 730 d of main housing 730. Thatis, the pair of hub bearings 742 is positioned axially between andengages (1) spacer ring 748 and (2) a combination of stationary carrier790 and a ring gear of a planetary gear arrangement.

Spacer ring 748 is positioned between the first bearing of the pair ofhub bearings 742 and main housing 730 in a manner similar to thatdescribed above with regard to FIG. 14. Spacer ring 748 includes a bodyand a rim extending transversely therefrom. A hub seal and a spindleseal (e.g., an O-ring seal) may engage the spacer ring 748 to facilitatecreation of the fluid seals. For example, the spacer ring 748 comprisesa compression face for the spindle seal and a running surface for thehub seal. The spindle seal is positioned between flange 730 d of themain housing 730 and the spacer ring 748. The hub seal 528 (as shown inFIG. 14) is positioned radially between and engages the spacer ring 748and an inner surface of the output hub.

Although only partially illustrated for clarity, the two-stage planetarygear arrangement of this optional configuration is substantially similarto the previously described planetary gear arrangement 650. For example,the two-stage planetary gear arrangement is housed within an output huband includes a ring gear that is fixed to the output hub. A plurality offirst stage planetary gears is driven by a first stage sun gear. Thefirst stage planetary gears are supported on support pins of a planetarygear carrier and are meshed with the first stage sun gear and the ringgear. Planetary gear carrier is drivingly engaged to second stage sungear 763, which in turn drives second stage reduction gears 782. Thesecond stage reduction gears 782 are meshed with second stage sun gear763 and the ring gear. The first stage planetary gears and the secondstage reduction gears 782 cooperatively drive the ring gear and, inturn, the output hub. Additionally, a hub cap or gear cover is coupled(e.g., threadably) to the output hub to cover the planetary geararrangement and bear against the ring gear. In turn, the ring gear bearsagainst the pair of hub bearings 742, thereby forcing the pair of hubbearings 742 to bear against the output hub in order to prevent and/orotherwise deter axial movement of the output hub.

An example reduction drive assembly comprises a housing that comprises afirst housing defining a brake housing compartment, a motor statorhousing, and a brake end cap defining a cylindrical volume. The examplereduction drive assembly comprises a motor assembly that comprises amotor disposed in the motor stator housing and an output shaft coupledto and driven by the motor. The example reduction drive assemblycomprises a planetary gear assembly driven by the output shaft. Theexample reduction drive assembly comprises an electric brake assemblythat comprises a brake rotor disposed within the brake housingcompartment and engaged to the output shaft, one or more statorsdisposed within the brake housing compartment adjacent to the brakerotor, a plug movably disposed in the cylindrical volume, a springdisposed within the cylindrical volume and configured to be compressedby the plug to apply a spring biasing force for pressing at least one ofthe one or more stators against the brake rotor, and an electric brakecoil positioned adjacent to at least one of the one or more stators, theelectric brake coil configured to electromagnetically move at least oneof the one or more stators away from the brake rotor when energized.

In some examples, the electric brake assembly further comprises a washerpositioned between and engaging the spring and at least one of the oneor more stators to facilitate application of the spring biasing force toat least one of the one or more stators.

In some examples, the plug is threadably coupled to the brake end capvia threading in a threaded aperture of the cylindrical volume tofacilitate loosening of the plug to reduce the spring biasing force. Insome such examples, the threading enables the plug to be positioned at alocation relative to the spring that causes the spring to bedecompressed to eliminate the spring biasing force.

In some examples, the one or more stators includes a first stator andsecond stator, the brake rotor is positioned between the first statorand the second stator, the second stator is positioned between the brakerotor and the spring, and the first stator is formed of high-carbonsteel to limit an amount of wear caused by the brake rotor and toprevent an electromagnetic force of the electric brake coil from movingthe first stator. In some such examples, the second stator is formed oflow-carbon steel, is thicker than the first stator, and is positionedadjacent to the electric brake coil to facilitate the electromagneticforce in moving the second stator.

In some examples, the one or more stators includes a first stator and asecond stator between which the brake rotor is positioned, the firsthousing further defines a first groove and a second groove, the firststator includes a first tab received by the first groove to preventrotation of the first stator, and the second stator includes a secondtab received by the second groove to prevent rotation of the secondstator. In some such examples, the first and second tabs and the firstand second grooves are stepped to facilitate the second stator in beingpositioned between the brake rotor and the spring.

In some examples, the electric brake coil, when energized, applies anelectromagnetic force that is greater than the spring biasing force toat least one of the one or more stators to release the at least one ofthe one or more stators from the brake rotor.

In some examples, the brake end cap defines a circumferential slot inwhich the electric brake coil is housed.

An example electric brake assembly for a planetary reduction drivecomprises a first housing defining a brake housing compartment, firstand second stators disposed within the brake housing compartment, and arotor disposed within the brake housing compartment between the firstand second stators. The rotor has a spline engaging an output shaft of amotor. The example electric brake assembly comprises a brake end capcoupled to the first housing and defining a cylindrical volume, a plugmovably disposed in the cylindrical volume of the brake end cap, aspring disposed within the cylindrical volume of the brake end cap andcompressed by the plug to apply a spring biasing force for pressing thesecond stator against the rotor, and an electric brake coil positionedadjacent to the second stator to electromagnetically pull the secondstator away from the rotor when energized.

In some examples, the electric brake assembly further comprises a washerpositioned between and engaging the spring and the second stator tofacilitate application of the spring biasing force to the second stator.

In some examples, the plug is threadably coupled to the brake end capvia threading in a threaded aperture of the cylindrical volume tofacilitate loosening of the plug to reduce the spring biasing force.

In some examples, first stator is formed of high-carbon steel to limitan amount of wear caused by the rotor and to prevent an electromagneticforce of the electric brake coil from moving the first stator. In somesuch examples, the second stator is formed of low-carbon steel, ispositioned adjacent to the electric brake coil, and is thicker than thefirst stator to facilitate the electromagnetic force in moving the firststator.

In some examples, the first housing defines a first groove and a secondgroove, the first stator includes a first tab received by the firstgroove to prevent rotation of the first stator, and the second statorincludes a second tab received by the second groove to prevent rotationof the second stator.

In some examples, the electric brake coil, when energized, applies anelectromagnetic force that is greater than the spring biasing force tothe second stator to release the second stator from the rotor.

An example electric brake assembly for a planetary reduction drivecomprises a housing defining a brake housing compartment and first andsecond grooves and a first stator disposed within the brake housingcompartment. The first stator includes a first tab received by the firstgroove to prevent rotation of the first stator. The example electricbrake assembly comprises a second stator disposed within the brakehousing compartment. The second stator includes a second tab received bythe second groove to prevent rotation of the second stator. The exampleelectric brake assembly comprises a rotor disposed within the brakehousing compartment between the first and second stators. The rotor hasa spline to engage an output shaft of a motor. The example electricbrake assembly comprises an electric brake coil positioned adjacent tothe second stator to electromagnetically pull the second stator awayfrom the rotor when energized. The first and second tabs and the firstand second grooves are stepped to facilitate positioning of the secondstator between the brake rotor and the electric brake coil.

In some examples, the second tab extends radially beyond the first taband the second groove is larger than the first groove.

In some examples, the housing further defines ribs that furtherfacilitate positioning of the first and second stators within the brakehousing compartment.

An example reduction drive assembly comprises a motor assemblycomprising a motor coupled to and driving an output shaft. The examplereduction drive assembly comprises a planetary gear assembly thatcomprises a first gear carrier comprising a first plate and a pluralityof projections extending therefrom. The first plate defines a pluralityof first support openings. The planetary gear assembly comprises asecond gear carrier defining a plurality of second support openings anda plurality of joint openings. The plurality of joint openings receivethe plurality of projections to couple the first and second gearcarriers. The planetary gear assembly comprises a sun gear coupled to anend of the output shaft and disposed between the first and second gearcarriers and a plurality of planet gears disposed around the sun gearbetween the first and second gear carriers. Each of the plurality ofplanet gears has a carrier pin. Each carrier pin is received by one ofthe plurality of first support openings and one of the plurality ofsecond support openings to retain the planet gears between the first andsecond gear carriers.

In some examples, each carrier pin is received by one of the pluralityof first support openings and one of the plurality of second supportopenings via press fit to retain a respective one of the plurality ofplanet gears between the first and second gear carriers.

In some examples, each of the plurality of projections is swaged tosecure the first gear carrier to the second gear carrier via a swagedconnection.

In some examples, the sun gear defines an axial opening having aninterior spline that receives an exterior spline at the end of theoutput shaft to couple the sun gear to the output shaft.

In some examples, the first gear carrier further comprises a pluralityof first protrusions extending from the first plate and from which theplurality of projections extend and the second gear carrier comprises aplurality of second protrusions that define the plurality of jointopenings. In such examples, the plurality of first protrusions and theplurality of second protrusions extend around the sun gear and theplanet gears to enable the first and second gear carriers to coupletogether.

An example planetary gear assembly comprises a first gear carriercomprising a first plate and a plurality of projections extendingtherefrom. The first plate defines a plurality of first supportopenings. The example planetary gear assembly comprises a second gearcarrier coupled to the first gear carrier. The second gear carrierdefines a plurality of second support openings and a plurality of jointopenings. The plurality of joint openings receive the plurality ofprojections to couple the first and second gear carriers together. Theexample planetary gear assembly comprises a sun gear disposed betweenthe first and second gear carriers and coupled to an end of a outputshaft of a motor, a plurality of planet gears disposed around andengaging the sun gear between the first and second gear carriers, and aplurality of carrier pins configured extending axially from theplurality of planet gears. The plurality of carrier pins are received bythe plurality of first support openings and the plurality of secondsupport openings to retain the plurality of planet gears between thefirst and second gear carriers.

In some examples, the plurality of projections are integrally formedwithin the first plate to enable the first gear carrier to be coupled tothe second gear carrier without separate fasteners.

In some examples, the plurality of carrier pins, the plurality of firstsupport openings, and the plurality of second support openings are sizedto enable the plurality of carrier pins to be received by the pluralityof first support openings and the plurality of second support openingsvia press fit.

In some examples, the first gear carrier defines a first plurality ofrelief slits. In such examples, each of the first plurality of reliefslits is formed in one of the plurality of first support openings todeter cracks from forming when the carrier pin of a respective one ofthe plurality of planet gears is received via press fit. In some suchexamples, the second gear carrier defines a second plurality of reliefslits. In such examples, each of the second plurality of relief slits isformed in one of the plurality of second support openings to detercracks from forming when the carrier pin of a respective one of theplurality of planet gears is received via press fit.

In some examples, each of the plurality of projections is swaged tosecure the first gear carrier to the second gear carrier via a swagedconnection.

In some examples, the sun gear defines a first axial opening having aninterior spline for coupling to the output shaft of the motor. In suchexamples, the first gear carrier or the second gear carrier defines asecond axial opening that enables the output shaft of the motor toextend to the sun gear positioned between the first and second gearcarriers.

In some examples, each of the plurality of planet gears comprises afirst stage gear and a second stage gear adjacent the first stage gear.In such examples, the second stage gear has a smaller outer diameterthan that of the first stage gear. In some such examples, the firststage gear of each of the plurality of planet gears is meshed with thesun gear.

In some examples, the first gear carrier further comprises a pluralityof first protrusions extending from the first plate and from which theplurality of projections extend and the second gear carrier comprises aplurality of second protrusions that define the plurality of jointopenings. In such examples, the plurality of first protrusions and theplurality of second protrusions extend around the sun gear and theplurality of planet gears disposed between the first and second gearcarriers to enable the first and second gear carriers to coupletogether. In some such examples, each of the plurality of projectionsextends from a respective one of the plurality of first protrusions andeach of the plurality of second protrusions defines a respective one ofthe plurality of joint openings.

An example method for assembling a planetary gear assembly comprisesextending carrier pins axially through respective planet gears,positioning the planet gears around a sun gear such that the planetgears engage the sun gear, and positioning the planet gears and the sungear between a first gear carrier and a second gear carrier. The firstgear carrier comprises projections and defining a plurality of firstsupport openings. The second gear carrier defines a plurality of secondsupport openings and a plurality of joint openings. The example methodcomprises retaining the planet gears between the first and second gearcarriers by extending the carrier pins into the plurality of first andsecond support openings. The example method comprises fixedly couplingthe first gear carrier to the second gear carrier without separatefasteners by extending the projections of the first gear carrier intothe plurality of joint openings of the second gear carrier.

In some examples, extending the carrier pins into the plurality of firstand second support openings comprises press fitting the carrier pinsinto the plurality of first and second support openings.

In some examples, coupling the first and second gear carriers togetherfurther comprises swaging the projections of the first gear carrier uponextending the projections through the plurality of joint openings of thesecond gear carrier.

Some examples further comprise coupling the sun gear to an end of anoutput shaft of a motor. In such examples, the sun gear comprises aninterior spline that engages an exterior spline of the output shaft forcoupling the sun gear to the output shaft.

Some examples further comprise, for each of the planet gears, coupling afirst stage gear to a second stage gear via slip or press fit. In suchexamples, the second stage gear has a smaller diameter than the firststage gear. In some examples, positioning the planet gears around thesun gear includes meshing the first stage gear of each of the planetgears with the sun gear.

An example electrical connector for a reduction drive assembly comprisesa connector body and a plurality of pins disposed within the connectorbody. The plurality of pins comprises one or more motor pins to conductpower to an electric motor, one or more brake pins to conduct power toan electric brake coil, and one or more sensor pins electricallyconnected to a sensor board for control of the electric motor.

In some examples, the connector body includes threads for threadedcoupling to a jam nut to couple the connector body to an electricalcompartment cover.

In some examples, the one or more motor pins include a first pin for afirst phase of the electric motor, a second pin for a second phase ofthe electric motor, and a third pin for a third phase of the electricmotor.

In some examples, the one or more brake pins include a power pin and aground pin.

In some examples, the one or more sensor pins include a first pin for afirst Hall-effect sensor, a second pin for a second Hall-effect sensor,a third pin for a third Hall-effect sensor, a fourth pin for atemperature sensor, a fifth pin for grounding the sensor board, and asixth pin for supplying power to the sensor board.

Some examples further comprise a brake connector coupled to the electricbrake coil and electrical wiring connecting the brake connector to theone or more brake pins.

Some examples further comprise a board connector coupled to the sensorboard and electrical wiring connecting the board connector to the one ormore sensor pins.

In some examples, the connector body defines one or more aperturesthrough which the one or more motor pins are configured to extend. Insome such examples, the one or more motor pins are detachable from theconnector body through the one or more apertures. In some examples, theone or more motor pins are fixed to the connector body. In someexamples, the one or more brake pins and the one or more sensor pins arefixed to the connector body.

An example electric connection assembly of a reduction drive assemblycomprises an electrical compartment integrally formed with a housing ofthe reduction drive assembly and an electrical compartment coverdefining a mounting opening and removably coupled to the electricalcompartment. The example electric connection assembly comprises anelectrical connector that is housed in the electrical compartment,partially extends through the mounting opening, and is mounted to thecompartment cover. The electrical connector comprises a connector bodyand a plurality of pins disposed within the connector body. Theplurality of pins comprises motor pins to conduct power to an electricmotor, brake pins to conduct power to an electric brake coil, and sensorpins electrically connected to a sensor board for control of theelectric motor.

Some examples further comprise fasteners for coupling the electricalcompartment cover to the electrical compartment.

In some examples, the electrical compartment cover includes one or moreguard walls adjacent to the mounting opening to protect the electricalconnector. In some such examples, to protect the electrical connector,the one or more guard walls have a height that extends beyond theelectrical connector. In some such examples, the one more guard wallsare spaced apart from the mounting opening by a distance that providesaccess to the electrical connector to enable a person to attach ordetach the electrical connector from the electrical compartment cover.

Some examples further comprise an outer gasket positioned between theelectrical compartment and the electrical compartment cover. Some suchexamples further comprise an inner gasket that engages an inner surfaceof the electrical compartment cover about the mounting opening to form aseal between the electrical connector and the electrical compartmentcover. In some such examples, the electrical compartment cover definesan outer groove in which the outer gasket is at least partiallypositioned. In some such examples, the electrical compartment coverincludes a perimeter rim that defines an interface surface and theelectrical compartment defines a mating surface. In such examples, theinterface surface and the mating surface are configured to limitcompression of the outer gasket positioned between the electricalcompartment and the electrical compartment cover. Further, in some suchexamples, the perimeter rim of the electrical compartment cover isconfigured to overlap with a raised seal surface of the electricalcompartment to facilitate alignment between the electrical compartmentcover and the electrical compartment and to protect the outer gasketpositioned between the electrical compartment cover and the electricalcompartment.

In some examples, the connector body defines one or more aperturesthrough which the motor pins extend, the motor pins are detachable fromthe connector body through the one or more apertures, and the brake pinsand the sensor pins being fixed to the connector body.

In some examples, the connector body defines one or more aperturesthrough which the motor pins extend. In such examples, the motor pins,the brake pins, and the sensor pins are fixed to the connector body.

An example reduction drive assembly comprises a housing that comprises aspindle having a first end and a second end opposite the first end. Thespindle defines an aperture that extends axially between the first endand the second end. The housing comprises a flange extending radiallyoutward from the second end of the spindle. Outer surfaces of thespindle and the flange form at least one fillet corner. The examplereduction drive assembly comprises a motor output shaft coupled to anddriven by a motor. The motor output shaft extends through the apertureof the spindle. The example reduction drive assembly comprises aplanetary gear assembly that comprises a sun gear coupled to and drivenby the motor output shaft and a plurality of planet gears meshed withand driven by the sun gear. Each of the plurality of planet gears has afirst stage gear and a second stage gear. The example reduction driveassembly comprises a fixed ring gear coupled to the first end of thespindle and housing the second stage gear. The fixed ring gear is meshedwith the second stage gear of each of the plurality of planet gears. Theexample reduction drive assembly comprises an output hub, a rotatingring gear coupled to the output hub and meshed with the first stage gearof each of the plurality of planet gears to cause the output hub torotate about the spindle of the housing, a set of bearings positionedradially between an outer surface of the spindle and an inner surface ofthe output hub and axially between the fixed ring gear and the flange ofthe housing to facilitate rotation of the output hub, and a spacer ringpositioned between the spindle flange and the set of bearings andadjacent the at least one fillet corner to reduce stress of the housing.

In some examples, the set of bearings includes a first bearing and asecond bearing that contact each other. In such examples, the firstbearing further contacts the spacer ring and the second bearing furthercontacts the fixed ring gear.

In some examples, an outer surface of each bearing of the set ofbearings contacts the inner surface of the output hub and an innersurface of each bearing of the set of bearings contacts the outersurface of the spindle.

Some examples further comprise a third bearing disposed in the apertureof the spindle about the motor output shaft and adjacent an innersurface of the spindle.

In some examples, the fixed ring gear is disposed in the output hub andthe planetary gear assembly is at least partially disposed in the outputhub.

In some examples, the output hub has a first hub end that extends beyondthe fixed ring gear and a second hub end that extends toward the flangeof the housing. Some such examples further comprise a hub cap coupled tothe first hub end to cover the planetary gear assembly. Further, in somesuch examples, the hub cap defines through holes and the first hub enddefines threaded holes that receive threaded fasteners to couple the hubcap to the output hub.

In some examples, the first end of the spindle defines threaded holes,the fixed ring gear defines mounting holes, and the mounting holes alignwith the threaded holes to receive threaded fasteners that couple thefixed ring gear to the spindle.

In some examples, the flange of the housing defines mounting holes forattaching the reduction drive assembly to a frame structure.

An example reduction drive assembly comprises a housing that comprises aspindle having a first end and a second end opposite the first end. Thespindle defines an aperture that extends axially between the first endand the second end. The housing comprises a flange extending radiallyoutward from the second end of the spindle. The example reduction driveassembly comprises a motor output shaft coupled to and driven by amotor. The motor output shaft extends through the aperture of thespindle. The example reduction drive assembly comprises a planetary gearassembly that comprises a sun gear coupled to and driven by the motoroutput shaft and a plurality of planet gears meshed with and driven bythe sun gear. Each of the plurality of planet gears has a first stagegear and a second stage gear. The example reduction drive assemblycomprises a fixed ring gear coupled to the first end of the spindle andhousing the second stage gear. The fixed ring gear is meshed with thesecond stage gear of each of the plurality of planet gears. The examplereduction drive assembly comprises an output hub, a rotating ring gearcoupled to the output hub and meshed with the first stage gear of eachof the plurality of planet gears to cause the output hub to rotate aboutthe spindle of the housing, a set of bearings positioned radiallybetween an outer surface of the spindle and an inner surface of theoutput hub and axially between the fixed ring gear and the flange of thehousing to facilitate rotation of the output hub, and a spacer ringincluding a body and a rim that extends from the body. The spacer ringis positioned between and engages the set of bearings and the housing toreduce stress of the housing.

Some examples further comprise an O-ring seal positioned between theflange of the housing, the body of the spacer ring, and the rim of thespacer ring.

Some examples further comprise a hub seal positioned radially betweenand engaging the spacer ring and the inner surface of the output hub.Some such examples further comprise a first retaining ring and a secondretaining ring. In such examples, the hub seal is positioned axiallybetween the first and second retaining rings. Further, in some suchexamples, the first retaining ring engages the inner surface of theoutput hub. Further, in some such examples, the second retaining ring ispositioned between the hub seal and one bearing of the set of bearings.In such examples, the second retaining ring is positioned in a retainingring groove defined along the inner surface of the output hub.

In some examples, the set of bearings includes a first bearing and asecond bearing that contact each other. In such examples, the firstbearing further contacts the spacer ring and the second bearing furthercontacts the fixed ring gear.

An example reduction drive assembly comprises a spindle having a firstend and a second end opposite the first end. The spindle defines anaperture that extends axially between the first end and the second end.The example reduction drive assembly comprises a motor output shaftcoupled to and driven by a motor. The motor output shaft extends throughthe aperture of the spindle. The example reduction drive assemblycomprises an output hub configured to rotate about the spindle and aplanetary gear assembly housed within the output hub. The planetary gearassembly comprises a ring gear fixed to the output hub, a first stagesun gear coupled to and driven by the motor output shaft, a second stagesun gear, a planetary gear carrier engaged to the second stage sun gearand having support pins, first stage planetary gears each of which issupported by a respective one of the support pins of the planetary gearcarrier and meshed with the first stage sun gear and the ring gear,carrier pins extending from the first end of the spindle, and secondstage reduction gears each of which is rotationally mounted on arespective one of the carrier pins and is meshed with the second stagesun gear and the ring gear.

In some examples, the first stage planetary gears and the second stagereduction gears are configured to cooperatively drive the ring gear todrive the output hub.

Some examples further comprise a set of bearings positioned radiallybetween an outer surface of the spindle and an inner surface of theoutput hub. In such examples, the set of bearings comprises a firstbearing and a second bearing that are arranged axially in a side-by-sidemanner. Some such examples further comprise a housing that comprises thespindle and a flange. In such examples, the flange extends radiallyoutward from the second end of the spindle. Further, some such examplesfurther comprise a spacer ring positioned between the first bearing andthe flange. Further, some such examples further comprise fastenersreceived by bores at the first end of the spindle. Moreover, in somesuch examples, the fasteners engage the second bearing to clamp the setof bearings against the flange of the housing. In some such examples,the set of bearings is positioned axially between a spacer ringpositioned adjacent to the second end of the spindle and fastenersextending from the first end of the spindle.

Some examples further comprise a hub cap threadbly coupled to the outputhub to cover the planetary gear assembly. In some such examples, whencoupled to the output hub, the hub cap is configured to push the ringgear to deter axial movement of the output hub relative to the spindle.

Some examples further comprise a magnet carrier mounted within theaperture at the first end of the spindle. In some such examples, themagnet carrier retains a plurality of magnets. In some such examples,the magnet carrier includes a lip that extends beyond the first end ofthe spindle. Such examples further comprise at least one washerpositioned between and engaging at least one of the second stagereduction gears and the lip of the magnet carrier to retain the magnetcarrier within the aperture at the first end of the spindle.

An example reduction drive assembly comprises a spindle having a firstend and a second end opposite the first end. The spindle defines anaperture that extends axially between the first end and the second end.The example reduction drive assembly comprises a motor output shaftcoupled to and driven by a motor. The motor output shaft extends throughthe aperture of the spindle. The example reduction drive assemblycomprises an output hub configured to rotate about the spindle and aplanetary gear assembly housed within the output hub. The planetary gearassembly comprises a ring gear fixed to the output hub, a first stagesun gear coupled to and driven by the motor output shaft, a second stagesun gear, a planetary gear carrier engaged to the second stage sun gearand having first support pins, first stage planetary gears each of whichis supported by a respective one of the first support pins of theplanetary gear carrier and meshed with the first stage sun gear and thering gear, a stationary carrier coupled to the first end of the spindleand having second support pins, and second stage reduction gears each ofwhich is rotationally mounted on a respective one of the second supportpins and is meshed with the second stage sun gear and the ring gear.

In some examples, the first end of the spindle defines a pilot tofacilitate the stationary carrier in coupling to the first end of thespindle.

Some examples further comprise a set of bearings positioned radiallybetween an outer surface of the spindle and an inner surface of theoutput hub. In such examples, the set of bearings comprises a firstbearing and a second bearing that are arranged axially in a side-by-sidemanner. Some such examples further comprise a housing that comprises thespindle and a flange. In such examples, the flange extends radiallyoutward from the second end of the spindle. Further, some such examplesfurther comprise a spacer ring positioned between the first bearing andthe flange. Further, in some such examples, the stationary carrierengages the second bearing to press the set of bearings against theflange of the housing. In some such examples the set of bearings ispositioned axially between a spacer ring that is adjacent to the secondend of the spindle and the stationary carrier that is adjacent to thefirst end of the spindle.

Some examples further comprise a hub cap coupled to the output hub tocover the planetary gear assembly. In some such examples, when coupledto the output hub, the hub cap is configured to push the ring gear todeter axial movement of the output hub relative to the spindle.

Some examples further comprise a spacer and a washer positioned betweenthe second stage sun gear and the first end of the spindle.

While specific embodiments of the invention have been described indetail, it will be appreciated by those skilled in the art that variousmodifications and alternatives to those details could be developed inlight of the overall teachings of the disclosure. Accordingly, theparticular arrangements disclosed are meant to be illustrative only andnot limiting as to the scope of the invention which is to be given thefull breadth of the appended claims and any equivalent thereof.

What is claimed is:
 1. A reduction drive assembly, comprising: a housing comprising: a first housing defining a brake housing compartment; a motor stator housing; and a brake end cap defining a cylindrical volume; a motor assembly comprising: a motor disposed in the motor stator housing; and an output shaft coupled to and driven by the motor; a planetary gear assembly driven by the output shaft; and an electric brake assembly comprising: a brake rotor disposed within the brake housing compartment and engaged to the output shaft; one or more stators disposed within the brake housing compartment adjacent to the brake rotor; a plug movably disposed in the cylindrical volume; a spring disposed within the cylindrical volume and configured to be compressed by the plug to apply a spring biasing force for pressing at least one of the one or more stators against the brake rotor; and an electric brake coil positioned adjacent to at least one of the one or more stators, the electric brake coil configured to electromagnetically move at least one of the one or more stators away from the brake rotor when energized.
 2. The reduction drive assembly of claim 1, wherein the electric brake assembly further comprises a washer positioned between and engaging the spring and at least one of the one or more stators to facilitate application of the spring biasing force to at least one of the one or more stators.
 3. The reduction drive assembly of claim 1, wherein the plug is threadably coupled to the brake end cap via threading in a threaded aperture of the cylindrical volume to facilitate loosening of the plug to reduce the spring biasing force.
 4. The reduction drive assembly of claim 3, wherein the threading enables the plug to be positioned at a location relative to the spring that causes the spring to be decompressed to eliminate the spring biasing force.
 5. The reduction drive assembly of claim 1, wherein the one or more stators includes a first stator and second stator, the brake rotor is positioned between the first stator and the second stator, the second stator is positioned between the brake rotor and the spring, the first stator is formed of high-carbon steel to limit an amount of wear caused by the brake rotor and to prevent an electromagnetic force of the electric brake coil from moving the first stator.
 6. The reduction drive assembly of claim 5, wherein the second stator is formed of low-carbon steel, is thicker than the first stator, and is positioned adjacent to the electric brake coil to facilitate the electromagnetic force in moving the second stator.
 7. The reduction drive assembly of claim 1, wherein the one or more stators includes a first stator and a second stator between which the brake rotor is positioned, the first housing further defines a first groove and a second groove, the first stator includes a first tab received by the first groove to prevent rotation of the first stator, the second stator includes a second tab received by the second groove to prevent rotation of the second stator.
 8. The reduction drive assembly of claim 7, wherein the first and second tabs and the first and second grooves are stepped to facilitate the second stator in being positioned between the brake rotor and the spring.
 9. The reduction drive assembly of claim 1, wherein the electric brake coil, when energized, applies an electromagnetic force that is greater than the spring biasing force to at least one of the one or more stators to release the at least one of the one or more stators from the brake rotor.
 10. The reduction drive assembly of claim 1, wherein the brake end cap defines a circumferential slot in which the electric brake coil is housed.
 11. An electric brake assembly for a planetary reduction drive, comprising: a first housing defining a brake housing compartment; first and second stators disposed within the brake housing compartment; a rotor disposed within the brake housing compartment between the first and second stators, the rotor having a spline engaging an output shaft of a motor; a brake end cap coupled to the first housing and defining a cylindrical volume; a plug movably disposed in the cylindrical volume of the brake end cap; a spring disposed within the cylindrical volume of the brake end cap and compressed by the plug to apply a spring biasing force for pressing the second stator against the rotor; and an electric brake coil positioned adjacent to the second stator to electromagnetically pull the second stator away from the rotor when energized.
 12. The electric brake assembly of claim 11, further comprising a washer positioned between and engaging the spring and the second stator to facilitate application of the spring biasing force to the second stator.
 13. The electric brake assembly of claim 11, wherein the plug is threadably coupled to the brake end cap via threading in a threaded aperture of the cylindrical volume to facilitate loosening of the plug to reduce the spring biasing force.
 14. The electric brake assembly of claim 11, wherein the first stator is formed of high-carbon steel to limit an amount of wear caused by the rotor and to prevent an electromagnetic force of the electric brake coil from moving the first stator.
 15. The electric brake assembly of claim 14, wherein the second stator is formed of low-carbon steel, is positioned adjacent to the electric brake coil, and is thicker than the first stator to facilitate the electromagnetic force in moving the first stator.
 16. The electric brake assembly of claim 11, wherein the first housing defines a first groove and a second groove, the first stator includes a first tab received by the first groove to prevent rotation of the first stator, and the second stator includes a second tab received by the second groove to prevent rotation of the second stator.
 17. The electric brake assembly of claim 11, wherein the electric brake coil, when energized, applies an electromagnetic force that is greater than the spring biasing force to the second stator to release the second stator from the rotor.
 18. An electric brake assembly for a planetary reduction drive, comprising: a housing defining a brake housing compartment and first and second grooves; a first stator disposed within the brake housing compartment, the first stator includes a first tab received by the first groove to prevent rotation of the first stator; a second stator disposed within the brake housing compartment, the second stator includes a second tab received by the second groove to prevent rotation of the second stator; a rotor disposed within the brake housing compartment between the first and second stators, the rotor having a spline to engage an output shaft of a motor; and an electric brake coil positioned adjacent to the second stator to electromagnetically pull the second stator away from the rotor when energized, wherein the first and second tabs and the first and second grooves are stepped to facilitate positioning of the second stator between the rotor and the electric brake coil.
 19. The electric brake assembly of claim 18, wherein the second tab extends radially beyond the first tab and the second groove is larger than the first groove.
 20. The electric brake assembly of claim 18, wherein the housing further defines ribs that further facilitate positioning of the first and second stators within the brake housing compartment. 